C. Liu1, K. Li1, J. Pruszynski2, C. Heid2, P. Bajona2, J. Murala2, M. A. Wait2, L. Huffman2 1University Of Texas Southwestern Medical Center,Medical School,Dallas, TX, USA 2University Of Texas Southwestern Medical Center,Department Of Cardiovascular And Thoracic Surgery,Dallas, TX, USA
Introduction: Lung transplantation is the definitive treatment for end-stage lung diseases. Selection of lung transplant patients includes an evaluation of body mass index (BMI), as obesity is a relative contraindication. However, BMI changes may occur during the waiting list period, resulting in lower or higher BMI at the time of transplant. Previous single center studies have assessed the effects of waiting period BMI change on short-term outcomes of lung transplantation. The aim of this study is to assess the long-term outcomes of waiting list BMI changes.
Methods: The internal prospectively maintained Society of Thoracic Surgery (STS) transplant database and electronic medical records were reviewed for single and bilateral lung transplants between February 2004 and December 2018. Patients were classified as underweight (< 20 kg/m2), obese (> 30 kg/m2), or control (20-30 kg/m2). Obese and underweight patients were then further stratified based on whether they lost (-) or gained (+) weight during the waiting list period. The primary endpoint was overall mortality. Secondary outcomes were initial intensive care unit (ICU) hours, initial mechanical ventilator (MV) hours, initial hospital length of stay (LOS), and a composite of in-hospital complications. Kaplan-Meier curves and log rank test were used to compare overall mortality between the BMI groups. A modification of the z-test using Greenwood's formula for variance was used to compare the survival rate at 1, 3, and 5 years. Kruskal-Wallis, chi square, and Fisher exact test were used to compare the distribution of secondary variables. Statistical significance was indicated by p < 0.05.
Results: A total of 644 cases were included in this study. The groups and their sizes are as follows: underweight and lost weight (BMI < 20, -), 46/644 (7%); underweight and gained weight (BMI < 20, +), 59/644 (9%); obese and lost weight (BMI > 30, -), 80/644 (12%); and obese and gained weight (BMI > 30, +), 32/644 (5%). 423/644 (66%) patients were in the control group (BMI 20-30). Log rank test indicated an association between overall survival and change in BMI from listing to transplantation (p = 0.01). There was also a significant difference in the initial MV hours between the BMI cohorts (p = 0.014).
Conclusion: Obese and underweight patients who trended toward control BMI (20-30 kg/m2) during the waiting list period had better overall survival rates than obese and underweight patients who trended away. The waiting list period presents an opportunity for obese and underweight patients to improve their preoperative health status and long-term outcomes.
